With 39 people dead and at least 40 injured, the attack on an Istanbul nightclub cast a dark shadow over New Year’s Eve celebrations globally, sparking an emotional outpouring online amongst the celebrations.

“We don't need a new year, we need a new humanity,” one mournful tweet read with the hashtag 'Reina', the popular nightclub in the city's Besiktas district where the attack occurred.

Echoing the reaction to recent attacks including Paris and Dallas, many also asked people to “pray for Istanbul.”

No terror group has yet claimed responsibility for the attack, which involved at least one gunman, who was initially reported to have been wearing a Santa Claus costume. While there have been rumors of a second attacker, officials have said they are currently only hunting one suspect.

Although the culprits and their motives are not yet known, for a number of netizens, they have already laid blame at the foot of Islamic State (IS, formerly ISIS/ISIL), while others have simply blamed the entire religion of Islam.

“Evil never rests. Or should I say the religion of peace never rests,” one tweet read, while Mustafa Akyol, a New York Times Opinion writer, vented online: “May their murderer, probably an ISIS terrorist, go to hell.”

Russian President Vladimir Putin offered words of sympathy to those affected and said Russia will always remain Turkey’s partner in fighting terrorism.

“It is impossible to imagine a more cynical crime than the killing of civilians during the New Year,” Putin said. “But terrorists are devoid of any idea of human morals. Our common duty is to decisively strike back against the terrorist aggression.”

The White House has also condemned the attack, describing it as "horrific.""That such an atrocity could be perpetrated upon innocent victims, many of whom were celebrating New Year's Eve, underscores the savagery of the attackers," a statement read.

British Prime Minister Theresa May has yet to issue a statement on the attack, while foreign secretary Boris Johnson tweeted: “Thoughts with Turkey after cowardly act of terrorism in Istanbul nightclub attack. We stand shoulder to shoulder with our Turkish friends.”

Thoughts with #Turkey after cowardly act of terrorism in #Istanbul nightclub attack. We stand shoulder to shoulder with our Turkish friends